Locking arrangement for blading of axial-flow turbines and compressors



Nov. 24, 1953 L. HAWORTH ETAL 2,660,413

. LOCKING ARRANGEMENT FOR BLADING OF AXIAL-FLOW TURBINES AND COMPRESSORSFile d Jan. 29, 1951 3 Sheets-Sheet 3 52 a 4 1 an I I a MVEhra/(S 51 50&

LIONEL HAWORTH JAMES A- PETRI Patented Nov. 24, 1953 LOCKING ARRANGEMENTFOR BLADING OF AXIAL-FLOW TURBINES AND COM- PRES SORS Lionel Haworth andJames Alexander Petrie, Littieover, England, assignors to Rolls-RoyceLimited, Derby, England, a British company Application January 29, 1951,Serial No. 208,282

Claims priority, application Great Britain February 3, 1950 Claims. 1

This invention provides an improved locking arrangement for blading ofaxial-flow turbines and compressors. It is concerned with turbine orcompressor rotor assemblies of the kind (hereinafter referred to as thekind described) in which the blades are retained in position on theperiphery of a rotor disc by means of co-operating features on theblades and disc, which features extend circumferentially of theperipheral portion of the disc and permit the blades to be engaged inthe disc by sliding in a generally axial sense with respect to the rotordisc axis.

Assemblies of the kind described include those in which the blades areprovided with root attachments of the fir-tree or bulb-root type; incertain cases with root attachments of these types, the mean centrelines of the co-operating formations in the periphery of the disc may,although extending in the generally axial sense, be skewed relative tothe axis of the disc, so that the assembly of the blades is effectedalong these skewed lines.

It will be appreciated that in turbine and compressor rotor assembliesof the kind indicated it is necessary to make provision to restrain theblades against sliding in the disc after assembly, and hitherto it hasbeen common practice to provide a tang formation on the apex portion ofthe root attachment of the blade, i. e. that end of the root attachmentremote from the blade profile, which tang formation is bent over whenthe blade is mounted in the disc and provides an axial abutmentrestraining the blade from leaving the disc by sliding in the generallyaxial sense. In another known arrangement, it has been the practiceafter assembly to peen the root of the blade and the disc in the regionof the root fixing. Both these known arrangements sufier from thedisadvantage that on dismantling of the turbine or compressor rotorassembly by removing the blades from the rotor disc, the rootattachments of the blades are necessarily damaged, and generally in thecase of high performance engines the blading at least cannot be usedagain.

It is an object of the present invention to provide a simple arrangementfor the locking blades in position in turbine or compressor assembliesof the kind described, which permits assembly and dismantling of theblades without their be ing damaged, so enabling them to be re-usedafter dismantling.

According to the present invention there is provided a turbine orcompressor assembly wherein the rotor disc and a blade element carriedthereon are provided with adjacent axial projections each having arecess formed therein, which recesses are positioned to come oppositeone another when the blade element is properly in position in the disc,and wherein there is provided a locking member which is engaged in bothrecesses to be placed in shear by restraining disengaging movement ofthe blade element from the disc.

In one preferred arrangement, the axial projection on a blade element isradially outside the projection on the disc, the recess in theprojection on the blade element faces inwardly, the recess in theprojection on the disc faces outwardly and the recesses together form acircumierentially-extending tunnel to receive the locking memben,Conveniently the locking member has a substantially rectangular sectionand each recess has a substantially triangular section, the recessestogether forming a tunnel of substantially rectangular section toreceive the locking member. Moreover in the preferred arrangement, theprojection on the disc is an axial flange and the flange has formedtherein an outwardly facing continuous groove to afford a recess toco-operate with the inwardly facing recesses on the projections of aplurality of blade elements.

The locking member for such an arrangement may comprise a thick centralportion which is partly received in the recess in the projection of theassociated blade element and is partly received in the recess in theprojection on the disc, and end portions of reduced thickness permittingthem to be bent over to retain the locking member in the recesses afterassembly.

The projections on the blade elements may also be formed to affordabutments to limit slid- 1ing of the blade elements in the assemblydirecion.

An embodiment of the invention will now be described as applied in agas-turbine, the descrip tion referring to the accompanying drawings inwhich:

Figure l is an axial section through the gas turbine,

Figure 2 is a substantially enlarged view of the root attachmentportions of blades forming part of the gas turbine rotor,

Figure 3 is a View (to the same scale as Figure 2 and partly in axialsection) of the root attachment portion of a blade,

Figure 4 is a greatly enlarged section through means including a lockingmember for retaining a blade against detachment from the rotor,

Figures 5 and 6 illustrate a convenient method of manufacturing one formof the locking member.

Figures 7, 8 and 9 are a side elevation, an end elevation and a planview respectively to an enlarged scale of a locking member as producedby the method illustrated in Figures and 6 and prior to use, and

Figure 10 is a perspective view of a locking member such as isillustrated in Figures 7, 8 and 9, as it would appear if removed fromthe rotor without being damaged.

Referring now to Figure 1, there is illustrated a form of gas-turbinecomprising a pair of rotor discs Illa, Hib which carry at theirperipheries rotor blades I2. The turbine also comprises stationarystructure including a casing 3, a first nozzle guide vane assembly I i,a second nozzle guide vane assembly i5, and inner stationary structure18, ll. These parts may be of any convenient construction.

The rotor blades 42 are illustrated as being of the kind having each inone piece therewith an outer shroud 12a and at its radially inner end acombined inner shroud and root attachment portion I21), the details ofwhich will be seen from Figures 2 to 4 to which reference will now bemade.

Each portion [22) comprises an inner shroud forming part 28 of the rootand connected by a stem 21 to a root attachment part 22, illustrated asa root attachment of the fir tree type.

The root attachments 22 are engaged in correspondingly shaped channels23 broached in the periphery of the rotor disc iii, and in thisparticular embodiment, the fir-tree root attachments 22 and theirchannels 23 are skewed with respect to the axis of the turbine rotorIii.

As is usual the blades I2 are mounted on the disc periphery by slidingthe fir-tree root attachment 22 into the co-operating channel 23.

The blades I2 are retained against disengagement from the disc :9 in aradial direction by the co-operating shoulders of the fir-treeformations.

This invention provides means to retain the blades against detachmentfrom their channels by sliding of the root attachments 22 in thechannels.

This means comprises in this embodiment a projection M on each bladeformed on the upstream-facing surface of the root attachment part 22 atits apex. The projection 2c is hooked to afford aradially-inwardly-extending portion having an axially-directed abutmentsurface 25 which bears against the axially-directed surface of the disci0 adjacent the bottom of the channel 23. This abutment surface 25limits the extent to which a blade can slide relatively to its channel23 in one direction, in this case from the high-pressure to the lowpressure side of the disc [0.

The projection 23 is also undercut, Figure 4, to afford a recess 26 ofroughly triangular section extending circumferentially across theprojection 24 and facing inwardly towards the rotor axis.

The disc ii) is provided with an axially-extending flange 21 lyingslightly radially inwards of the bottoms of the channels 23 and of theprojections 24, and this flange 21 has machined in it a continuous,radially-outwardly-facing groove 28 of substantially triangular section.

The groove 28 lies opposite the recesses 25 in the projections 24 whenthe surfaces 25 abut the disc l0, and the groove 28 and recesses 26oooperate to aiford a series of substantially rectangular tunnels, onefor each blade.

Each tunnel receives a rectangular wire looking member 30 which acts torestrain movement of the blade in a direction to detach the blade l2from the disc it, that is in this case in a direction from the lowpressure side of the disc towards the high pressure side.

The locking members 30 are conveniently formed with tabs 3|, 32 ofreduced strength at each end, which tabs are bent upwardly as shown inFigures 2, 3 and 10, one on each side of the projection 24 to retain thelocking member in position in the tunnel. Conveniently, one tab 3! isbent up before the locking member 39 is placed in position, which iseffected by placing the locking member in groove 28 between twoprojections as indicated in chain lines in Figure 2 and then sliding itinto position in the tunnel, thereafter bending up the tab 32.

The locking member of this embodiment is illustrated by itself inFigures 7 to 19.

The wire locking members 38 are preferably manufactured from continuousstrip or wire material by a milling operation involving reducing thethickness of the strip or wire to form the tabs 3|, 32 andsimultaneously parting the strip or wire. Such a milling operation isillustrated in Figures 5 and 6 in which 34 indicates the milling cutter,35 indicates the continuous strip or wire of rectangular section, andthe parted locking members are indicated by the same references as areemployed in the remainder of the description. As will be seen the cutterM has a profile afiording two side cutting faces 34a to mill a channelin the strip or wire 35 and a central cutting face 34?) to part thestrip or wire at the centre of the channel. The axis of the cutter 34may be skewed relative to the strip or wire 34 so that, when the rootattachment 22 is skewed relative to the turbine, the thicker centralpart of the locking member will be of parallelogram form to conform tothe shape of the recess 26 in the projection 24, and the tabs 3!, 32will when bent up lie flush against the circumferentially directed facesof the projection 28.

By arranging the locking member 39 on the high pressure side of the discIf], the locking member will not be required to support heavy shearloads in operation since the loads on the blade tend to move it from thehigh pressure side of the disc towards the low pressure side.

One important advantage of this invention is that blades can beassembled and dismantled without damaging the blade of the disc, sincein order to remove a blade, it is only necessary to remove the lockingmember and then draw the blade free from the disc. Thus the blades can,if desired, be replaced in the disc after inspection.

We claim:

1. An axial-flow turbine or compressor assembly comprising a rotor discwith a plurality of slots extending across the disc periphery from oneface of the disc to the other face of the disc; a plurality of bladeelements, each blade element having a root attachment portion engaged ina corresponding one of said slots; radially-outwardly-facing shoulderson the circumferential faces of said root attachment portions;radiallyinwardly-facing shoulders on the circumferential walls of saidslots in co-operating abutment with said outwardly-facing shoulders toretain said root attachment portions against radially outwarddisplacement from the slots: and means to restrain disengagement of theroot attachment portions of the blade elements from the slots in thedisc by sliding lengthwise of the slots, which means comprises axialprojections on said root attachment portions, said axial projectionsbeing formed with recesses having axially-facing abutment walls, anaxial extension on said disc which axial extension has a co-operatingrecess with axially-facing abutment walls, the recesses in said axialprojections being positioned in the projections to be aligned with theco-operating recess in said axial extension when said root attachmentportions are properly positioned in said slots, and a plurality oflocking members, said axial projections on the blade elements beingradially outside said axial extension on the disc, the recesses in saidaxial projections facing radially inwardly, and having said co-operatingrecess in said axial extension facing radially outwardly andco-operating with the recesses in said axial projections to formcircumferentially-extending tunnels each to receive one of said lockingmembers, whereby each locking member is loaded in shear through theaxially-facing abutment walls by forces tending to cause lengthwisesliding of the associated root attachment portion in the correspondingslot in either direction.

2. A turbine or compressor assembly as claimed in claim 1, wherein thelocking members have a substantially rectangular section and each recesshas a substantially triangular section, the recesses together forming atunnel of substantially rectangular section to receive the lockingmemher.

3. A turbine or compressor assembly as claimed in claim 2, wherein theaxial extension on the disc is an axial flange and the flange has formedtherein an outwardly-facing continuous groove to afford saidco-operating recess.

4. An axial-flow turbine or compressor assembly comprising a rotor discwith a plurality of slots extending across the disc periphery from oneface of the disc to the other face of the disc; a plurality of bladeelements, each blade element having a root attachment portion engaged ina corresponding one of said slots; radiallyoutWardly-facing shoulders onthe circumferential faces of said root attachment portions;radially-inwardly-facing shoulders on the circumferential walls of saidslots in co-operating abutment with said outwardly-facing shoulders toretain said root attachment portions against radially outwarddisplacement from the slots; and means to restrain disengagement of theroot attachment portions of the blade elements from the slots in thedisc by sliding lengthwise of the slots, which means comprises axialprojections on said root attachment portions, said axial projectionsbeing formed with recesses having axially-facing abutment walls, anaxial extension on said disc which axial extension has a cooperatingrecess with axially-facing abutment walls, the recesses in said axialprojections being positioned in the projections to be aligned withthecooperating recess in said axial extension when said root attachmentportions are properly positioned in said slots, and a plurality oflocking members, each locking member comprising a thick central portionwhich is partly received in the recess in the axial projection of theassociated blade element and is partly received in said co-operatingrecess in the axial extension on the disc, and end portions of reducedthickness permitting them to be bent over to retain the locking memberin the recess after assembly, whereby each locking member is loaded inshear through the axially-facing abutment walls by forces tending tocause lengthwise sliding of the associated root attachment portion inthe corresponding slot in either direction.

5. An axial-flow turbine or compressor assembly comprising a rotor discwith a plurality of slots extending across the disc periphery from oneface of the disc to the other face of the disc; a plurality of bladeelements, each blade element having a root attachment portion engaged ina corresponding one of said slots; radially-outwardly-facing shoulderson the circumferential faces of said root attachment portions;radiallyinwardly-facing shoulders on the circumferential walls of saidslots in co-operating abutment with said outwardly-facing shoulders toretain said root attachment portions against radially outwarddisplacement from the slots; and means to restrain disengagement of theroot attachment portions of the blade elements from the slots in thedisc by sliding lengthwise of the slots, which means comprises axialprojections on said root attachment portions, said axial projectionsbeing formed with recesses having axially-facing abutment walls, anaxial extension on said disc, which axial extension has a co-operatingrecess with axially-facing abutment walls, the recesses in said axialprojections being positioned in the projections to be aligned with theco-operating recess in said axial extension when said root attachmentportions are properly positioned in said slots, and a plurality oflocking members, each said locking member projecting into both saidco-operating recess and an aligned recess in one of said axialprojections thereby to be loaded in shear through the axially-facingabutment walls by forces tending to cause lengthwise sliding of theassociated root attachment portion in the corresponding slot in eitherdirection, each said axial projection also comprising an abutmentcooperating with the face of the disc radially inwards of the slots tolimit sliding of the associated root attachment portion in theassociated slot in the direction of said abutment.

LIONEL HAWORTI-I. JAMES ALEXANDER PE'I'RIE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,072,457 Herr Sept. 9, 1913 1,890,581 Kohler Dec. 13, 1932FOREIGN PATENTS Number Country Date 537,121 Great Britain 1941 606,151Great Britain 1948 612,097 Great Britain 1948 618,011 Great Britain 1949

